Recent Work on Photoemission and Dark Emission Problems

The image-dissector, multiplier phototube as a detector in analytical emission spectroscopy

“…Commercial photocathodes are categorized by standard spectral response numbers, and responses of several of the more common types are illustrated in Figure 1. Each surface has a different thermal work function (55) and accordingly, presents a different dark current under equivalent sets of conditions. Dark current is measured at the anode of the photomultiplier with no radiation incident on the cathode and is thus a function of gain, cathode area and cathode composi tion.…”

“…In general, surfaces, such as the S-1 type (Ag-O-Cs), which respond to red radiation, exhibit dark currents that are much greater than those for the S-11 or S-20 response types. However, the S-20 surface (Sb-K-Na-Cs; multialkali) which has much better red response and higher quantum efficiency than the S-11 type (Sb-Cs on Mn-MnO layer), has a thermionic emission level that is equal to (55) or lower than (54) that of the S-11.…”

“…response, diminishes about an order of magnitude for every 20°K temperature decrease, and dark current is reduced by a factor of 10 for each 10°K temperature decrease. That such an approach to reduce dark current is commonly attempted appears well documented in the publication of many photomultiplier cryostat designs (49,(50)(51)(52)(53)(54)(55)(56)(57)(58)(59) and applications to spectroscopic studies (15,(70)(71)(72)(73)(74)(75) and astronomy (76,77).…”